You want honesty? I don't know the girl you're talking about....but I'll take a guess. It's possible that she finds self-flagilation boring and unpleasant. Moreover, she may feel that if she is forced to hand you the metaphorical stick that you want to use to beat the hell out of yourself....she's somehow gotten involved in a process of ego-destruction she'd rather not be even tertiarily responsible for.

Basically, some girls have this instinctive need to avoid the passive agressive....and I really think that you should, well, let them get on with it. They're obviously not the person you're looking for.